Channel acquisition is the process of finding and acquiring access to a communication channel. When WiMAX devices initialize (e.g. when they are turned on), they begin a channel scanning process. Channel scanning is the process of searching through multiple radio channels to find signals that indicate a channel is available on which to communicate. The WiMAX device will typically have a stored list of frequency channels for it to scan in order to reduce the amount of scanning time. These frequency channels may be preprogrammed by or for a WiMAX system operator so the WiMAX device will initially try to connect to a specific WiMAX system.
When the WiMAX device has found one or more WiMAX radio channels, the device will decode the channel and look for packets of data that have a frame control header that contains a downlink channel description (DCD) message and an uplink channel description (UCD) message. The DCD message contains parameters that are necessary or that will assist it to access the device in receiving information from the downlink channel on the communication system. The UCD message provides the device with the parameters that are necessary to access the communication system.
